Use of wireless networks such as wireless local area networks (WLANs) is becoming widespread. With the proliferation of WLANs, network security is also becoming more and more important. WLANs present important network security concerns.
A WLAN may be ad hoc, in that any client device (referred to herein as a client) may communicate directly with any other client, or have an infrastructure in which a client can only communicate with another client via an access point in which a client can only communicate with another client via an access point device (AP). Problems specific to WLANs arise from wireless clients requesting access to the various APs. Often in a deployment of a WLAN environment, AP cells' coverages are overlapped to achieve maximum RF coverage to reduce non-service spots. Wireless clients can move between APs, and thus change the RF environment of the WLAN depending on their location. Additionally, WLANs are often required to grow with increased demand as more and more clients require service from the WLAN. Expanding the WLAN requires reconfiguring equipment, adding APs, and placing APs in locations that do not conflict with other APs or otherwise complicate managing the WLAN.
Another WLAN management challenge is the detection of clients that should not have access to the WLAN, such as in the case where a wireless client interferes with the WLAN simply by occupying space that is peripheral to the WLAN. This may happen when a wireless device is legitimately deployed in an area near the WLAN, such as in an adjacent office building or parking lot, or simply when someone with a wireless client device enters the WLAN coverage area with a legitimate purpose, such as making a delivery or visiting the WLAN site for other reasons. In such situations, reconfiguration of the WLAN is often necessary, and APs again must be repositioned or reconfigured.
Yet another WLAN challenge occurs when changes are required in the placement of wireless clients served by the WLAN. For example, one or more floors in an office building or several buildings are included in a typical WLAN coverage area. Rearrangement of furniture, placement of walls, doors, and RF sources such as copiers, computers, telephone systems and the like can affect the coverage area by contributing to “black holes,” in which interference and transmission path loss prevent APs from being able to detect each other and require the APs to be placed in different locations to adequately serve their respective wireless clients.
In a WLAN with power save clients, multicast and broadcast packets are transmitted immediately following the transmission of a deliver traffic indication message (DTIM). The DTIM occurs at regular intervals with a frequency related to the beacon interval of each AP. If two APS have the same beacon interval and time period it is possible for the two APs to become synchronized with respect to when the DTIM occurs. If these same two APs are transmitting on the same channel it is possible for a client to be in a location such that it receives the transmissions from each of the APs at an equivalent signal level. If the two APS cannot detect each other's transmissions they may each find the channel to be clear after performing a clear channel assessment and transmit mulitcast and/or broadcast traffic simultaneously following their respective DTIMs. The net result of this is that the client remains in a multicast/broadcast black hole for as long as the client remains in the given location and the DTIM timing remained synchronized.
Thus, deployment, expansion, and day-to-day management of a WLAN are nontrivial tasks that require significant time, effort and skills. There is a heartfelt need for methods and equipment to efficiently manage these tasks and provide WLAN managers with information needed to make management decisions.